Bolass other abilities are strong too, but the drawing two cards effect is never dead
Headless Rider is an easy card to sleep on, but the fact that it triggers on itself dying as well is huge
Not only does it provide treasures and creature tokens every turn, it also gives you pseudo-card draw
Goldspan Dragon will give you the mana to cast bigger and bigger spells each time it attacks, and your opponents will have to pay a price to remove it, too
Pteramander, Spectral Sailor, and Brineborn Cutthroat do offer some of that Mono-Blue Aggro touch, but for the most part its looking like the usual suspects of cantrips, counterspells, and card advantage are the story of the blue column
Call to the Kindred seems like the perfect fit for a deck like this provided you can make it around to your next turn with it still enchanting one of your Slivers